1. Field of the Invention
The present invention relates to a process for producing (meth)acrylic acid. The term “(meth)acrylic acid” as used herein means acrylic acid or methacrylic acid.
2. Description of the Related Art
In general, acrylic acid and methacrylic acid are useful raw materials widely used as the raw materials of chemical products, and various processes for their production have been proposed. For example, acrylic acid is produced by the gas phase catalytic oxidation of propylene and/or acrolein. Japanese Patent Laid-open Publications Nos. 2001-520213, 2004-359614, 2004-359615, and 2005-511776 disclose processes in which an acrylic acid-containing gas obtained by a gas phase catalytic oxidation method is absorbed into an absorbent to provide an acrylic acid containing solution, followed by distillation and/or crystallization steps, thereby obtaining purified acrylic acid. Japanese Patent Laid-open Publications Nos. 2001-516737, 2002-539104, and 2002-509903 disclose processes of directly obtaining crude acrylic acid from an acrylic acid-containing gas by fractional condensation.
These production processes have various improvements for the purpose of producing acrylic acid with high efficiency. In particular, regarding the method employing absorption with a solvent, there have been proposed, for the purpose of obtaining higher purity acrylic acid, a method of adding a polymerization inhibitor to be used in the separation and purification step (see Japanese Patent Laid-open Publication No. 2001-520213), a method of improving the rate of absorption of acrylic acid (see Japanese Patent Laid-open Publication No. 2004-359614), and a method of carrying out the purification of acrylic acid easily and simply by the use of a high concentration acrylic acid containing solution. In addition, Japanese Patent Laid-open Publication No. 2005-511776 proposes a method of forming acrylic acid with high efficiency in the gas phase catalytic oxidation reaction.